Vol. 4
May Issue
Year 2003


in Vol. 4 - May Issue - Year 2003
Ultrasonic Impact Treatment enhances physical Properties of ferrous and non-ferrous Castings

Treatment of Machined Pulley

Treatment of Machined Roll

Treatment of Yoke

Treatment of Cylindrical Gear

Ultrasonic impact treatment of ferrous and non-ferrous components enhances physical properties such as surface hardness, corrosion-wear resistance, casting strength, and fatigue life.

The technology of using high  energy ultrasonics to modify surface and sub-surface properties of metallic parts was originally invented in Russia in 1968 by Dr. Efim Statnikov and used within their Naval and Aerospace programs since 1972.  The technology has been used to reduce welding stresses and deformation, introduce compressive stresses, increase corrosion-fatigue strength, improve surface finish properties, and specifically enhance the surface wear and contact fatigue properties. In this vein, ultrasonic impact technology (UIT) is being used on bridge weldings in the U.S. for bridge repairs, new bridge construction, and for improving reliability of many other machined and cast components. Testing done by renowned research institutes across the world has shown the results from UIT to be vastly superior to any of the other employed techniques for wear resistance and fatigue life enhancement.  With the introduction of UIT, welded high yield steel structures are a practical and realistic solution to previous structural integrity problems encountered when welding these steels.

The logical progression for applications of this technology led to the treatment of gears, shafts, wheels, brake components, and other cast or machined components that are subjected to severe cyclical loading during use.  In the case of gears, testing has been completed on treating the teeth and roots of bevel gear teeth.  The results of these tests show fatigue life enhancement of up to 15 times that of typical shot peening, while also improving surface finish in the treated areas and increasing the surface hardness.  The altered surface properties reduce the surface fatigue normally caused by micro surface defects whilst increasing resistance to contact fatigue.  Surface hardness levels increased from 54-56 HRc, after carburization, to 59-61 HRc after UIT, and surface finish improved from Ra 02.8-0.38 to Ra 0.15-0.18 microns after UIT treatment.

How UIT Works

The principle of UIT is based on instrumental conversions of harmonic oscillations of an acoustically tuned body into resonant impulses of ultrasonic frequency.  The acoustically tuned body is brought to resonance by energizing an ultrasonic transducer.  The energy generated from these high frequency impulses is imparted to the surface to be treated through the contact of specially designed steel pins.  These transfer pins are free to move axially between the resonant body and the treated surface.

Depending on the desired effects from the treatment, a combination of different frequencies and displacement amplitude is applied.  The frequencies range between 27 KHz and 55 KHz, with displacement amplitude of the resonant body between 22 and 50 microns.  The controlled action of the application allows one to define the exact combination of effects, including surface finish properties, enhanced corrosion resistance properties, compressive stress depth, etc.

The UIT technology can be applied to a wide variety of metals, including but not limited to, Steel, Iron, Aluminum, Inconel, Titanium, Stainless Steel, and Bronze, to name a few.  The technology is rapidly being accepted as a superior technique for enhancing fatigue properties of cast, machined, or welded components that are subject to fatigue failures during use, or need enhanced strength and hardness properties.  The mechanics of applying the technology allow integration with machining operations that include lathes, milling machines, or robotic systems.
The changes in physical properties created by UIT can enhance fatigue life of virtually any metallic part while adding additional beneficial surface and sub-surface condition enhancements.

At one Glance: Other results

Aluminum Castings:
Sealed surface defects and sub-surface porosity, increased surface hardess, and yielded strengths equal to forged components.  Increased hardness at the surface 38% and 23% at a depth of +2mm.

Bronze Castings:
Improved surface finish, increased surface hardness, and decreased corrosion failures in weld-repaired areas.  Hardness increased at a depth of +1.5mm by 20%.

Grey Iron Castings:
Brake drums demonstrated a 5-7 times increase in life before heat checking. Hardness increased by 10% at a depth of 1.5mm on drums, and for rotors, 37% at the surface and 12% at a depth of +1.5mm

Ductile Iron Castings:
Yokes demonstrated up to 7-9 times life.

Machined Steel Rolls:
48 to 50 HRc, increased hardness 16% at a depth of 1mm.

Author: Dan Spinner
For information:
Partner Program Manager
Apllied Ultrasonics
Tel: +1.205.951 1834
Fax: +1.205.951 3759
E-mai: dspinner@appliedultrasonics.com